This is a phase 1 study designed to determine the maximum tolerated dose of gemcitabine given concurrently with radiation therapy for locally advanced unresectable pancreatic cancer. Patients with unresectable adenocarcinoma of the pancreas are eligible. Gemcitabine will be administered week IV over 1/2 hour for five weeks. Toxicity is evaluated using RTOG and CTEP standard toxicity criteria. We have accrued four patients so far and we are at the initial dose level of 350 mg/m2.